Investigation of Abnormal VTH/VFB Shifts Under Operating Conditions in Flash Memory Cells With \Al2\O3 High-\kappa Gate Stacks.

\Al2\O3 high- \kappa stack is a strong candidate as the dielectric layer in Flash memory cells for technology generations beyond sub-20 nm. In this paper, the cause of abnormal VTH/VFB shift at low operating electric fields is investigated, i.e., VTH/VFB reduces at low positive gate biases and increases at low negative gate biases. It is found that this instability does not originate from the electrons trapping/detrapping from the gate nor from the dielectric relaxation. For the first time, extensive experimental evidences show that this shift is caused by as-grown mobile charges in \Al2\O3 layers generated by postdeposition annealing at 1000 ^\circ\C or above. Its impacts on program/erase windows and read/pass disturbance in Flash memory cells are also evaluated. [ABSTRACT FROM PUBLISHER]